A data input device such as a mouse includes a mechanism that tracks the movement of the mouse. The movement of the mouse is used to position an on-screen indicator (e.g., a cursor) as is desired by a mouse user. However, many conventional data input systems are not equipped to support cutting edge applications, such as graphics applications, that require three-dimensional tracking of the input device in order to position a three dimensional on-screen indicator among other shortcomings.
A conventional mouse can include a metal or plastic housing or casing and a ball that sticks out of the bottom of the casing. The mouse can be rolled on a flat surface, and can have one or more buttons on the top of the casing, and a cable that connects the mouse to a computer. As the ball is moved over the surface in any direction, a rotary sensor (electromechanical transducer) sends impulses to the computer that causes a mouse-responsive program to reposition an on-screen indicator (e.g., a cursor) on a display screen. The positioning is generally relative to some variable starting place. By noting the current position of the cursor on the display screen, a user can readjust the position of the on-screen indicator with precision by moving the mouse.
An optical mouse uses a light-emitting diode, an optical sensor, and digital signal processor (DSP) in place of the conventional mouse ball and electromechanical transducer discussed above. Movement is detected by sensing changes in reflected light, rather than by interpreting the motion of a rolling sphere.
The optical mouse takes microscopic snapshots of the surface upon which the mouse is positioned at a rate of more than 1,000 images per second. When the mouse is moved, the image of the surface changes. The tiniest irregularities in the surface can produce images that enable the sensor and DSP to generate usable movement data. The best surfaces reflect but scatter light, such as for example, a blank sheet of white drawing paper.
Conventional mouse systems have many shortcomings that are traceable to their aforementioned reliance on the use of mechanical balls and rotary sensors or optical pickups to determine position. Those devices that employ mechanical balls and rotary sensors invariably have moving parts that require cleaning. Moreover, devices that rely on optics require special surfaces in order for them to function properly. It should be appreciated that some surfaces do not permit the proper functioning of the sensor and DSP because the irregularities in the surfaces are too small to be detected, e.g., unfrosted glass. In addition, as discussed above, many conventional devices do not support cutting edge applications, such as graphics applications, that require three-dimensional tracking of the input device to position a three-dimensional on screen indicator.